1. Field of the Invention
The following description relates to an image display device and method capable of adjusting brightness.
2. Description of the Related Art
In general, image display devices serve to display image data, applied from a camera or imaging device, in a state of visible light which can be seen by people. Televisions or beam projectors belong to the image display devices. Recently, with the development of technology, researches on image display devices using LCD (Liquid Crystal Display) or PDP (Plasma Display Panel) are actively carried out.
In particular, since the LCD cannot emit light by itself, an image display device using the LCD requires a separate light source for LCD. As for the light source for LCD, a CCFL (Cold Cathode Fluorescent Lamp) is mainly used. In terms of characteristics of the CCFL, the brightness and lifespan thereof are inversely proportional to each other. That is, when the CCFL is driven by a high current so as to increase the brightness, the lifespan is reduced. On the contrary, to increase the lifespan, the CCFL should be driven by a low current. Therefore, it is difficult to achieve high brightness. In most cases, however, high brightness and a long lifespan are simultaneously requested, when the CCFL is applied to products.
Hereinafter, a conventional image display device using the LCD panel will be described with reference to accompanying drawings.
FIG. 1 is a block diagram of a conventional image display device.
As shown in FIG. 1, the conventional image display device includes an image display unit 110, a backlight driving unit 120, and a data drive 130.
The image display unit 110 is composed of an image display panel 111 and a backlight module 112 and is connected to the backlight driving unit 120 and the data drive 130. The image display unit 110 outputs image output data D, applied through the data drive 130, through the image display panel 111.
The backlight driving unit 120 generates a driving voltage C for driving the backlight module 112 so as to supply to the backlight module 112. The backlight module 112 is driven by the driving voltage C supplied from the backlight driving unit 120 so as to supply light to the image display panel 111 while maintaining constant brightness.
The data drive 130 delivers to the image display panel 111 the image output data D which is converted into data for outputting RGB image data applied from outside through the image display panel 111.
That is, to output the RGB image data, applied from outside, as visible light which can be seen by people, the image output data D converted by the data drive 130 is delivered to the image display panel 111. Further, to supply auxiliary light to the image display panel 111 which cannot emit light, the driving voltage C supplied through the backlight driving unit 120 is supplied to the backlight module 112 such that the RGB image data is displayed on the image display panel 111.
However, the conventional image display device has the following problems.
In the conventional image display device, a technique for high brightness and long-term lifespan is adopted, in which when an image should be displayed with high brightness or an external input is received from a user while the backlight module 112 is driven so as to display an image on the image display panel 111 with preset brightness, a high current is temporarily applied to the backlight module 112 such that an active region of the image display panel 111 with respect to the brightness is widened.
Further, when the image display panel 111 is used as the LCD, an amount of current used in the image display panel 111 differs depending on an image displayed on the image display panel 111. That is, in a case of the normally-white mode where liquid crystal molecules within the image display panel 111 are re-arranged in an electric-field direction with the application of voltage to the image display panel 111 such that incident light is cut off, the power consumption of the image display panel 111 is reduced, as the number of bright pixels increases in the image display panel 111. However, as the number of dark pixels increases, the power consumption of the image display unit 110 is increased.
To solve such a problem, a method is used in which a current value of the driving voltage C of the backlight module 112 interlocked with the image display panel 111 is controlled depending on the power consumption of the image display panel 111. When such a method is applied, an additional circuit should be implemented in such a manner that the conventional image display device fits into a variable range for controlling the brightness of the backlight driving unit 120 which detects the current consumed by the image display panel 111 and drives the backlight module 112.
Further, since all the images are controlled with the same brightness, power consumption increases in comparison with when the brightness should be controlled only for an image where the brightness control is required. As the brightness is adjusted, a brighter or darker image than an intended image may be output. Then, reliability of the image is degraded.